Fix These Selective Entry Maths Errors Before Exam Day
The 10 mistakes
Section 1 of the Victorian selective entry exam - Mathematics and Quantitative Reasoning - runs for 60 minutes and is usually the section students feel most confident about. That confidence can be a problem. Many students lose marks not because they do not know the maths, but because they make avoidable mistakes under pressure.
These are the 10 most common errors we see, why they happen, and exactly how to fix each one.
1 Not reading the question fully
Why it happens: Students see a familiar question type, assume they know what is being asked, and start solving before they have finished reading. The ACER exam is designed to punish this - questions often have a twist in the final line, such as "which is NOT true" or "find the difference" instead of "find the total."
The fix: Read every question twice before writing anything. On the second read, underline or circle the key instruction word (find, NOT, difference, least, greatest, approximately). This takes five seconds and prevents the most common source of lost marks on the entire exam.
2 Rushing mental arithmetic
Why it happens: Students try to do too many steps in their head to save time. A small calculation error early in a multi-step problem cascades through the entire solution, producing a wrong answer even though the method was correct.
The fix: Write down every calculation step, even simple ones. Mental maths is fine for single-step operations like 7 x 8, but anything involving two or more steps should be written out. The few seconds spent writing are far less costly than getting the wrong answer.
3 Forgetting units and labels
Why it happens: Students focus on the numerical calculation and forget to check whether the question asks for the answer in centimetres, metres, kilograms, hours, or another unit. Mixed-unit problems (such as converting minutes to hours, or millilitres to litres) are a common trap.
The fix: Before solving, write down the units the question asks for. After solving, check that your answer is in those units. When a problem involves mixed units (such as some values in cm and others in m), convert everything to the same unit before calculating.
4 Weak on fractions, ratios and percentages
Why it happens: These topics are heavily tested on the SEHS exam but are often under-practised. Many students are comfortable with basic fractions but struggle when problems involve comparing fractions with different denominators, converting between fractions and percentages, or using ratios to divide quantities.
The fix: Dedicate specific practice sessions to fractions, ratios and percentages - do not just include them as part of general maths practice. Master these core skills: finding common denominators, converting between fractions, decimals and percentages, simplifying ratios, and dividing a quantity in a given ratio. These come up repeatedly on the exam.
Not sure where your child's maths gaps are? The diagnostic test pinpoints exactly which areas need work.
Take the SK Diagnostic - Free5 Misreading graphs and tables
Why it happens: Graph and data interpretation questions require careful reading of axes, scales, legends and labels. Students often glance at a graph, estimate a value incorrectly, and then perform the right calculation on the wrong number. Bar graphs with non-zero starting axes and tables with multiple categories are especially tricky.
The fix: Before answering any graph question, identify three things: what the axes represent, what the scale increments are, and whether there is a legend or footnote. Point to each data value with your pencil and read it carefully. Never estimate when you can read an exact value.
6 Skipping working out
Why it happens: Some students believe that showing working wastes time, or that "smart" students should be able to solve problems in their head. In reality, skipping working leads to more errors, makes it impossible to check your method, and means you cannot identify where things went wrong.
The fix: Write clear, organised working for every multi-step problem. Even on multiple-choice exams where only the answer matters, your working is your safety net. If you have time to check at the end, you can quickly trace your steps. Neat working also helps you think more clearly during the problem itself.
7 Not checking answers
Why it happens: Students use all 60 minutes solving questions and leave zero time for checking. In a competitive exam where one or two marks can determine the outcome, this is a significant missed opportunity.
The fix: Budget your time so you have at least 5 minutes at the end for checking. During the check, do not just re-read your answers - actively verify them. For each answer, ask: "Does this make sense? Is the magnitude reasonable? Did I answer what was actually asked?" Quick sanity checks catch more errors than you would expect.
8 Poor time management
Why it happens: Students spend too long on difficult questions and then rush through easier ones at the end, making careless errors on questions they would normally get right. The SEHS exam is designed so that later questions are generally harder - getting stuck on question 15 and running out of time for the last 10 questions is a common disaster.
The fix: Follow the "one minute per question" rule as a guide. If a question is taking more than 90 seconds and you are not making progress, mark it, skip it, and come back to it after finishing the rest. Every question is worth the same marks - a correct answer on an easy question counts the same as a correct answer on a hard one. Get the easy marks first.
9 Not practising under exam conditions
Why it happens: Students practise maths questions at home with no time limit, no pressure and often with breaks between questions. When they face the real exam - 60 minutes, no calculator, no breaks, a room full of other students - the pressure causes a performance drop that has nothing to do with ability.
The fix: At least once a week, do a full timed practice session under real conditions. Set a timer for 60 minutes. No phone, no breaks, no calculator. Sit at a desk. Complete the whole paper in one sitting. The goal is to make exam conditions feel normal so that on the actual day, your child performs at their true level.
10 Ignoring quantitative reasoning
Why it happens: Many students and parents treat Section 1 as "the maths section" and focus all their preparation on traditional maths topics. But the section is called Mathematics and Quantitative Reasoning for a reason. QR questions test pattern recognition, number sequences, spatial reasoning and logical problem-solving - skills that are different from standard school maths.
The fix: Allocate dedicated practice time to quantitative reasoning. QR questions often look unfamiliar at first, but the underlying patterns are learnable with practice. Work through number sequences (find the rule), shape patterns (rotation, reflection, addition), and logical puzzles (if-then reasoning with numbers). Students who prepare for QR specifically gain a real advantage over those who only practise traditional maths.
Bringing it all together
None of these mistakes are about intelligence or ability. They are about habits - and habits can be changed with deliberate practice. The students who score highest on the maths section are not always the ones who know the most maths. They are the ones who read carefully, manage their time, show their working and check their answers.
The selective entry exam is competitive. Melbourne High School, Mac.Robertson Girls' High School, Nossal High School and Suzanne Cory High School all use the same ACER-administered test, and every mark matters. Eliminating these 10 common mistakes is one of the fastest ways to improve your child's score without learning any new content.
Study plan tip: Print this list and stick it on the wall above your child's study desk. Before every practice session, read through the 10 mistakes as a reminder. Awareness is the first step to elimination.
Practice resources on SK Edge Prep
- Maths Prep - Structured practice covering all SEHS maths topics with worked solutions and difficulty progression.
- Maths Builder - Generate unlimited maths practice questions tailored to your child's level, with instant feedback.
- SK Diagnostic - Free - 50 questions across all exam sections. Identifies specific maths weaknesses so you know exactly where to focus.
- SK Mock Tests - Full-length timed tests under real exam conditions. The closest thing to the actual SEHS exam experience.
Frequently asked questions
Recommended tools: Maths Prep QR Prep SK FREE Diagnostic Test SK Mock Tests